The invention relates to a power source with miniaturized SOFC fuel cells (SOFC: solid oxide fuel cell). The power source contains the fuel cells in the form of a multi-modular unit, in particular in the form of a stack, the volume of which is preferably less than 10−4 m3. The invention also relates to a method for operation of the power source as well as for uses for the power source.
Portable electronic devices are at a stage of development in which these devices are becoming increasingly complicated and are being integrated into systems which are more and more complex. Due to the increase in complexity the need for electrical energy for operating the devices or systems is growing all the time. Conventional power sources, which are re-loadable, reach the limits of their capacity. Therefore power sources with miniaturized fuel cells are suggested, with which the named limits of capacity can be exceeded. Since power sources of this kind have to be relatively small, it is difficult to use electrochemical processes, which take place at high temperatures. For this reason miniaturized fuel cells are being developed, which work with polymer membranes at low temperatures (cells of the type PEMFC: proton exchange membrane fuel cell). In membranes of this kind a minimum water content has to be maintained however. This requirement is difficult to fulfill. Hydrogen is used as a fuel, which is a disadvantage with regard to storage, since only relatively small energy densities are possible with stored hydrogen.
Due to the problems with the PEMFC fuel cells, SOFC fuel cells have also been suggested, in spite of the known difficulties (see for example WO 0243177). In these fuel cells the membranes are made of solid electrolytes, which only have sufficiently high ionic conductivity at temperatures higher than 500° C. Propane or butane, which advantageously have relatively high energy densities in liquid form, can be used as fuels for example.